1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device. More particularly, the present invention relates to a backlight unit capable of controlling a brightness and obtaining a high brightness, and an LCD device having the same.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) device serves to display a desired image on a screen by controlling an amount of light transmitted to a backlight unit by a plurality of liquid crystal cells arranged in a matrix form and a liquid crystal panel composed of a plurality of controlling switches for switching video signals to be supplied to each of the liquid crystal cells.
The related art backlight unit of an LCD device will be explained with reference to FIG. 1.
FIG. 1 is a schematic view showing a construction of a backlight unit in accordance with the related art.
In FIG. 1, the related art backlight unit comprises a light guide plate 11 for guiding light beam 51 having passed through a light introducing portion 20, a reflection plate 31 disposed below the light guide plate 11 for reflecting the light beam 51 passing through a lower surface and a lateral surface of the light guide plate 11 towards an upper surface of the light guide plate 11, a first diffusion sheet 33 for diffusing the light beam 51 having passed through the light guide plate 11, a first prism sheet 35 and a second prism sheet 37 for controlling a moving direction of the light beam 51 having passed through the first diffusion sheet 33, a second diffusion sheet 39 for diffusing the light beam 51 having passed through the first prism sheet 35 and the second prism sheet 37, and an LCD panel 41 for receiving the light beam 51 diffused through the second diffusion sheet 39.
The light introducing portion 20 is composed of a light emitting lamp 21 for generating the light beam 51, and a lamp housing 23 for mounting the light emitting lamp 21 and reflecting the light beam 51 of the light emitting lamp 22 to the light guide plate 11.
The light beam 51 of the light introducing portion 20 is uniformly moved towards an upper surface of the light guide plate 11 via printed patterns formed at a lower surface of the light guide plate 11 so as not to satisfy a total reflection of the light beam 51 in every direction. The light beam 51 having been transmitted to the lower surface and the lateral surface of the light guide plate 11 is reflected by the reflection plate 31 thus to be transmitted to the upper surface of the light guide plate 11. An unexplained reference numeral 13 denotes a light guide reflection pattern.
The light beam 51 having passed the light guide plate 11 is diffused to an entire region of the LCD panel by the first diffusion sheet 33.
The light beam 51 having passed the first prism sheet 35 and the second prism sheet 37 passes through the second diffusion sheet 39 thereby to be incident on the LCD panel 41.
However, the related art backlight unit of an LCD device has the following problems.
In a process that a light beam generated from the light emitting lamp is guided to the light guide plate via the light introducing portion, whereas a large amount of the light beam is introduced to the light guide plate near the light introducing portion, a lesser amount of the light beam is introduced to the light guide plate distant from the light introducing portion.
Accordingly, the light beam is not uniformly distributed on the entire light guide plate, but is distributed with a different amount.
Therefore, in the related art light guide plate, a lamp brightness is not stabilized and the brightness is not easily controlled.
Furthermore, in the related art backlight unit, only a single light emitting lamp is used thereby to have a limitation in implementing various kinds of brightness.